From: Alsoran Cole
Still not sure how to have outer alpha channels - are you saying I can have different textures on different sides of this now hollow cube?
Yes, you can have up to 10 different textures on a hollowed cube, since there are 10 sides.
If you select the cube, go to Edit mode, choose the texture tab and apply a texture, it will apply to all sides of the cube. If you open your texture folder and drag a texture to a single side of the cube (make sure you have not selected the whole cube first) then that texture will be applied to only the side you drag it to.
This technique also allows you to create objects that are transparent on one side and solid on the other. For instance, if you wanted a door that looks solid from outside but doesn't block your view of the sunset from your living room, then place a solid door texture on the outer side, and a transparent texture on the inner side. You wont be able to see the door from the inside, but it will look totally normal from the outside.
Another trick that I found is adding dark textures to sides that will adjoin each other. For instance, if you have two wall sections that will be stacked vertically and you are getting a small seam that looks like a dotted line between them, you can change the texture on the sides that touch to solid black. This makes the seam much less noticeable.
As for Alpha channels, you'll need a graphics editing package that supports 1) Alpha channel creation and 2) Export as 32-Bit .TGA (Targa). I use Adobe Photoshop, but there are others that will also work. Basically an Alpha channel is a mask that dictates what portions of the image are transparent. In Photoshop, select all the areas that you want to be solid, then "Save Selection As..." a new channel. When you go to the "Channels" tab, you will have RGB, Red, Green, Blue, and Alpha. You can then modify the alpha channel if you want more or less transparency. If you use the airbrush tool to spray a fine grey over the black parts of the alpha channel, you will reduce the transparency slightly. This is how you get windows that are more translucent, rather than totally clear.
Upload your new texture and drag it to the sides where you want windows. Keep in mind that if you want the windows on the inside too, you'll have to drag the texture to the inner-side of the cube as well.
From: Alsoran Cole
This is interesting stuff thank you so much - but I still want to learn a way to align textures - the feature would be a big help and release me from lots of close up inspections and fiddling.
To align textures, you can use the Texture offset tool on the Texture tab. One limitation of the Texture tool is that you cannot individually set the offset or number of repeats per face on a face-by-face basis. This means that if you have a prim of 10x10x.5, the repeats and offsets apply to the .5 meter side too. This can be very frustrating if you are trying to get an authentic look. There are a couple of work-arounds for this issue, but no good solutions that I have found as yet.
1) If the piece is a foundation piece (ie a 10x10x?? laying flat on the ground) simply stretch the prim vertically into the ground until it is 10x10x10. This will cause the offsets and repeats to apply equally on all sides and your texture will look perfect on the small section that sticks out of the ground.
2) Create a separate texture for the smaller sides, one that is sized and zoomed appropriately for your particular repeats and offsets. Apply this new texture to the smaller sides and presto. I haven't played with this too much, and I expect it will be time consuming and cost alot of L$, since theres a L$10 upload charge for each texture you upload.
3) Use the cut-cube method I described before to cut the cube in half. You can turn a hollowed cube into a single side, a corner with two sides, two corners and three sides, or anything in between.
Remember that perfection is difficult to achieve in SL without alot of time and effort. At times, its very frustrating. Remember that not all textures are created equal. Some simply won't align perfectly. This is particularly true if you simply take a picture of a pattern and import it as a .JPG. If the pattern isn't cropped properly to its repeating elements, then it will NEVER align correctly in SL.
Sorry for the long post, but I wanted to offer you all the options I have found so far. Again, these forums are a great resource and you may find other options if you search through older posts.
Good luck.
At the enges if you connect them perfectly you have stripping effects on the 0.5 edges. If you connect them so that the edges are not visible you have to offset with .001 so that you don't get the weird effects and if you do this it makes building a nightmare because snap to grid isn't an option - all blocks have to be 0.002 smaller etc